A particle image imaging device capable of imaging particles, and a particle image analyzing apparatus for analyzing the image of the particles are conventionally known (see e.g., EP1245945 and Japanese Laid-Open Patent Publication No. 2000-131616).
EP1245945 discloses a particle image analyzing apparatus for mixing a first suspension liquid in which transparent particles are dispersed in water and a second suspension liquid in which non-transparent particles are dispersed in water, thereby electrostatically attaching the non-transparent particles to the transparent particles to make the transparent particles non-transparent, and thereafter, imaging such non-transparent particles, and analyzing the imaged image. In such particle image analyzing apparatus, the degree of circularity of the transparent particle (morphological feature information) is calculated based on the imaged image.
Japanese Laid-Open Patent Publication No. 2000-131616 discloses a particle image imaging device including an zonal light generating unit (dark field illuminating unit) for converting the exit window from the light source to an zonal light, an inner surface reflection mirror for collecting and irradiating the zonal light to the particles dispersed in liquid, an objective lens for receiving the light from the illuminated particles at the inner side of the zonal light, an imaging lens arranged on the optical axis of the objective lens, and an imaging element for imaging the image formed by the imaging lens. The particles in the light scattering medium can be clearly imaged with the particle image imaging device of Japanese Laid-Open Patent Publication No. 2000-131616.
However, the particle image analyzing apparatus of EP1245945 requires for the preparation of the first suspension liquid in which the transparent particles are dispersed in water and the second suspension liquid in which the non-transparent particles are dispersed in water, and furthermore, mixing of the first suspension liquid and the second suspension liquid in order to image the transparent particles, and thus a great number of man hours and trouble are required in the imaging step of the transparent particles. The imaging step thus becomes complicating.
Furthermore, in Japanese Laid-Open Patent Publication No. 2000-131616, the laser light, which coherence is lowered by a coherence lowering element, is converted to the zonal light and then illuminated, and a translucent plate having a roughness of about the laser wavelength and a spatial filter in which the portion distant from the optical axis has higher light transmission than the optical axis are used to enable imaging of fine particles in the light scattering medium, but no description is made on analyzing the imaged particle image, in particular, no description is made on how the transparent particle image is analyzed in order to acquire the morphological feature information of the transparent particle.